The systematics of freshwater crayfish of the genus Cherax Erichson (Decapoda : Parastacidae) in eastern Australia re-examined using nucleotide sequences from 12S rRNA and 16S rRNA genes

Nucleotide sequence data were used to re-examine systematic relationships and species boundaries within the genus Cherax from eastern Australia. Partial sequences were amplified from the 12S (~365 bp) and 16S (~545 bp) rRNA mitochondrial gene regions. Levels of intra- and inter-specific divergence for Cherax species were very similar between the two gene regions and similar to that reported for other freshwater crayfish for 16S rRNA. Phylogenetic analyses using the combined data provided strong support for a monophyletic group containing 11 eastern Australian species and comprising three well-defined species-groups: the 'C. destructor' group containing three species, the 'C. cairnsensis' group containing four species and the 'C. cuspidatus' group containing two species. Cherax dispar and C. robustus are distinct from all other species and each other. In addition, two northern Australian and a New Guinean species were placed in the 'Astaconephrops' group, which is the sister-group to the eastern Australian Cherax lineage. Several relationships were clarified, including: the status of northern and southern C. cuspidatus as separate species; a close relationship between C. cairnsensis and C. depressus; the validity of C. rotundus and C. setosus as separate species and their close affinities with C. destructor; and the distinctiveness of the northern forms of Cherax. The analysis of the 12S rRNA and 16S rRNA data is highly concordant with the results of previous allozyme studies.

Complete mitochondrial DNA sequence of the Australian freshwater crayfish, Cherax destructor (Crustacea: Decapoda: Parastacidae): a novel gene order revealed

The complete mitochondrial DNA sequence was determined for the Australian freshwater crayfish Cherax destructor (Crustacea: Decapoda: Parastacidae). The 15,895-bp genome is circular with the same gene composition as that found in other metazoans. However, we report a novel gene arrangement with respect to the putative arthropod ancestral gene order and all other arthropod mitochondrial genomes sequenced to date. It is apparent that 11 genes have been translocated (ND1, ND4, ND4L, Cyt b, srRNA, and tRNAs Ser(UGA), Leu(CUN), Ile, Cys, Pro, and Val), two of which have also undergone inversions (tRNAs Pro and Val). The ‘duplication/random loss’ mechanism is a plausible model for the observed translocations, while ‘intramitochondrial recombination’ may account for the gene inversions. In addition, the arrangement of rRNA genes is incompatible with current mitochondrial transcription models, and suggests that a different transcription mechanism may operate in C. destructor.

Complete mitochondrial genome of the frillneck lizard (Chlamydosaurus kingii, Reptilia; Agamidae), another squamate with two control regions.

Using PCR, the complete mitochondrial genome was sequenced in three frillneck lizards (Chlamydosaurus kingii). The mitochondria spanned over 16,761bp. As in other vertebrates, two rRNA genes, 22 tRNA genes and 13 protein coding genes were identified. However, similar to some other squamate reptiles, two control regions (CRI and CRII) were identified, spanning 801 and 812 bp, respectively. Our results were compared with another Australian member of the family Agamidae, the bearded dragon (Pogana vitticeps). The overall base composition of the light-strand sequence largely mirrored that observed in P vitticeps. Furthermore, similar to P. vitticeps, we observed an insertion 801 bp long between the ND5 and ND6 genes. However, in contrast to P vitticeps we did not observe a conserved sequence block III region. Based on a comparison among the three frillneck lizards, we also present data on the proportion of variable sites within the major mitochondrial regions.

Real time RT-PCR analysis of housekeeping genes in human skeletal muscle following acute exercise

Studies examining gene expression with RT-PCR typically normalize their mRNA data to a constitutively expressed housekeeping gene. The validity of a particular housekeeping gene must be determined for each experimental intervention. We examined the expression of various housekeeping genes following an acute bout of endurance (END) or resistance (RES) exercise. Twenty-four healthy subjects performed either a interval-type cycle ergometry workout to exhaustion (~75 min; END) or 300 single-leg eccentric contractions (RES). Muscle biopsies were taken before exercise and 3 h and 48 h following exercise. Real-time RT-PCR was performed on ß-actin, cyclophilin (CYC), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and ß2-microglobulin (ß2M). In a second study, 10 healthy subjects performed 90 min of cycle ergometry at ~65% of O2 max, and we examined a fifth housekeeping gene, 28S rRNA, and reexamined ß2M, from muscle biopsy samples taken immediately postexercise. We showed that CYC increased 48 h following both END and RES exercise (3- and 5-fold, respectively; P < 0.01), and 28S rRNA increased immediately following END exercise (2-fold; P = 0.02). ß-Actin trended toward an increase following END exercise (1.85-fold collapsed across time; P = 0.13), and GAPDH trended toward a small yet robust increase at 3 h following RES exercise (1.4-fold; P = 0.067). In contrast, ß2M was not altered at any time point postexercise. We conclude that ß2M and ß-actin are the most stably expressed housekeeping genes in skeletal muscle following RES exercise, whereas ß2M and GAPDH are the most stably expressed following END exercise.